Device for microbiological examination of a sample of liquid under pressure and method for draining this device

ABSTRACT

This concerns a device whose filtering membrane ( 4 ) is gripped annularly at the periphery between a first member ( 9 ) forming part of an intake body ( 2 ) and a second member ( 32 ) forming part of a drainage body ( 3 ) with one out of the first member and second member having an elastomer seal ( 13 ) by means of which it comes into contact with the membrane ( 4 ), and whose locking means ( 7, 31 ) are adapted to allow the opening of the device by requiring only a separation movement between said first member ( 9 ) and said second member ( 32 ).  
     The drainage method proposes directly placing the device on a vacuum flask, the sealing with regard to the stopper of said flask being obtained by a rib ( 40 ) tapering towards its end.

[0001] The invention relates to the devices for microbiologicalexamination of a sample of liquid under pressure.

[0002] Such a device is already known through French patent 2 677 664,having an intake body, a filtering membrane and a drainage body. Theintake body has a reservoir, in one wall of which a liquid inputaperture is made, the membrane closing this reservoir by being welded onto the edge of the lateral wall of this reservoir, the drainage bodybeing designed to support the membrane on the opposite side from thereservoir and being provided with a liquid output aperture, the intakebody and the drainage body locking with one another by screwing byvirtue of integrally moulded thread elements.

[0003] The taking of a sample to be examined is performed by connectingthe input aperture of the reservoir of the intake body to a source ofliquid under pressure, so that the reservoir fills with this liquid,which can leave therefrom only through the filtering membrane, thisliquid being recovered from the other side of the membrane by thedrainage body and emptied therefrom through the output aperture.

[0004] In order to avoid the liquid which has passed through themembrane escaping from the drainage body somewhere other than throughthe output aperture, the intake body has, around the membrane, a flangeprovided with a lip coming to rest on the drainage body in order toobtain the required sealing.

[0005] This makes it possibly notably, for example by collecting theliquid emptied through the output aperture in a graduated container, toknow accurately the volume of the sample of liquid which has passedthrough the membrane.

[0006] EP 059 809 A discloses a disposable filtration unit for similarpurposes but where the sample of liquid is not under pressure. Thisdevice comprises as intake body an open ended shell, and, as drainagebody, a cup-shaped receptacle, a funnel-shaped support plate for thefiltering membrane and a support pad laid on the support plate which iscarried by an internal shoulder of the receptacle to which it can bepermanently attached by a suitable cement or by ultrasonic welding. Thelower end of the shell has a necked portion so that it can be receivedinto a rim of the receptacle, the axial length of the necked portion andits position within the rim being such that there is some axial distancebetween the top of the receptacle rim and an edge of the necked portion.A plurality of vertical ribs are formed integral with the shell. Theseribs have sufficient length to bridge this axial distance and can beattached to the upper end of the receptacle rim by ultrasonic welding soas to fix the shell to the receptacle. Because the attachment of theribs to the receptacle occurs only at spaced intervals about theperiphery of the receptacle, the ribs provides weak “breakaway” pointsso as to facilitate removal of the shell from the receptacle. In oneembodiment, a flat, annular gasket is disposed between the lower endface of the shell and the support plate, the inner periphery of thisgasket being squeezed between an inner foot of the shell and thefiltering membrane whereas the outer periphery of the gasket is squeezedby an outer foot of the shell and rests on the rim of the support plate,this gasket thus providing, on the one hand, a liquid-tight seal betweenthe shell and the filtering membrane and, on the other hand, anair-tight seal between the shell and the support plate. In otherembodiments, the support plate comprises an upstanding tongue which isreceived between the inner foot and the outer foot of the shell whereasthe flat, annular gasket is replaced by a gasket which has been put in aspace between the rim and the tongue of the receptacle.

[0007] U.S. Pat. No. 4,678,576 A discloses a device for similarpurposes, but not for a liquid under pressure. The disclosed devicecomprises, as intake body, an open ended upper body, and, as a drainagebody, a cup-shaped receptacle and a support plate, a locking rim beingfurther provided to lock the intake body and the drainage body. Thesupport plate is sandwiched between an upper collar portion of a collarincluded in the receptacle and an internal shoulder of a necked portionincluding the upper body, the ring being engaged respectively, by itsinternal thread, with the external thread of the lower portion of thecollar of the receptacle and, by an upper rim, with the lower externalshoulder of a split flange included in the upper body. In oneembodiment, two O-rings are provided respectively on one side and on theother of the support plate whereas in another embodiment, a singleH-shaped gasket is provided

[0008] The invention relates to a device of the same kind as knownthrough French patent 2 677 664, but simpler, more convenient and moreeconomical, both in manufacture and in use.

[0009] To that end it proposes a device for microbiological examinationof a sample of liquid under pressure, having an intake body, a filteringmembrane and a drainage body, said intake body having a reservoir, inone wall of which a liquid input aperture is made, said membrane closingsaid reservoir, said drainage body having means of supporting saidmembrane on the opposite side from said reservoir and a liquid outputaperture, said intake body and said drainage body having integrallymoulded mutual locking means; characterised in that said membrane isgripped annularly at the periphery between a first member forming partof said intake body and a second member forming part of said drainagebody with one out of said first member and said second member having anelastomer seal by means of which it comes into contact with saidmembrane, and in that said locking means are adapted to allow theopening of said device by requiring only a separation movement betweensaid first member and said second member, said locking means havingmeans of axial latching between the intake body and the drainage body,one out of the latter having at least one axially oriented latching tabwhile the other has means of receiving said latching tab, which extendsprojecting from the edge of a skirt forming part of that one out of saidintake body and said drainage body which includes it.

[0010] Thus, unlike the aforementioned earlier device known throughFrench patent 2 677 664, where the locking means are constituted bythread elements, the opening of the device according to the invention isperformed with no rotational movement between the intake body and thedrainage body.

[0011] The device according to the invention therefore makes it possibleto eliminate any risk of creasing the membrane at the time of openingthe device where it is then in the wet state.

[0012] Furthermore, the elastomer seal, although it is present only onone of the faces of the membrane, makes it possible to obtain sealing onboth faces of the membrane, that is to say both with the first memberand with the second member, from the simple fact that said members gripthe membrane, that is to say they are held close to one another, so thatit is not necessary, in order to close the device according to theinvention, to perform a rotational movement, unlike the above-mentionedearlier device known through French patent 2 677 664 which requires, sothat the sealing lip on the intake body is applied with the requiredintensity on the drainage body, that assembly is carried out by screwingwith a considerable torque.

[0013] The device according to the invention is therefore much simplerand more convenient to use than the above-mentioned earlier device knownthrough French patent 2 677 664, and is furthermore simpler tomanufacture, since there is no need, on the one hand, to make provisionfor achieving sealing between the membrane and the intake body bywelding, and, on the other hand, sealing around the membrane between theintake body and the drainage body, given that, in the device accordingto the invention, the gripping of the membrane between the first memberand the second member makes it possible to obtain these two instances ofsealing directly.

[0014] Thanks to the fact that the locking means have means of axiallatching between the intake body and the drainage body, the assembly ofthe device according to the invention is particularly simple, since itis sufficient to bring the intake body and the drainage body together inorder to lock them by latching.

[0015] It should be noted that the elastomer seal, on account of itselasticity, takes up the play necessary for enabling latching, so that,once assembled, the intake body and the drainage body are held with noaxial play with respect to one another.

[0016] The fact that one out of the intake body and the drainage bodyhas at least one axially oriented latching tab while the other has meansof receiving said latching tab, is preferred for reasons of simplicityand convenience, both in manufacture and in use.

[0017] Preferably, the membrane is held exclusively on account of itbeing gripped annularly at the periphery between said first member andsaid second member.

[0018] The manufacture and use of the device according to the inventionare thus particularly simple, since no operation such as the sealing ofthe membrane existing in the earlier device has to be implemented,while, after opening of the device according to the invention, themembrane, which is fixed neither to the first member nor to the secondmember, can be recovered directly, for example with sterile tweezers inorder to be put into culture in a conventional Petri dish.

[0019] Preferably again, said latching tab is connected to the remainderof that one out of said intake body and said drainage body whichincludes it, by a breakable zone.

[0020] The release of the locking means between the latching body andthe drainage body can thus be performed by simple breaking of thelatching tab, or even of a number of latching tabs if the deviceaccording to the invention has more than one.

[0021] According to other preferred characteristics, said drainage bodyhas a circular table provided at its centre with means of supportingsaid membrane and having, around said support means, a wall having asurface situated facing said elastomer seal, which forms part of saidintake body, said membrane being squeezed between said surface and saidseal.

[0022] This arrangement offers in effect the advantage of beingrelatively simple to implement and of obtaining excellent results asregards sealing.

[0023] According to other preferred characteristics, for the samereasons, said output aperture of the drainage body is in thecontinuation of the internal passage of an output pipe disposedcoaxially.

[0024] Preferably, said drainage body has, around said output pipe, anannular rib tapering towards its end.

[0025] This rib makes it possible in particular to drain the deviceaccording to the invention by placing it directly on a vacuum flask withsaid output pipe engaged in the central hole of the stopper of saidflask and said annular rib resting on this stopper.

[0026] The invention also relates, in a second aspect, to a method forthus draining the device according to the invention.

[0027] The explanation of the invention will now be continued with thedescription of an example embodiment, given below as a non-limitativeillustration, with reference to the accompanying drawings. In these:

[0028]FIG. 1 is an elevational view of a device in accordance with theinvention;

[0029]FIG. 2 is a sectional elevational view of this device;

[0030]FIGS. 3 and 4 are similar views but showing, respectively, onlythe intake body and the drainage body;

[0031]FIG. 5 is an enlargement of the part of FIG. 2 situated at thebottom right;

[0032]FIG. 6 is a partial sectional elevational view of the seal withwhich the intake body is provided;

[0033]FIG. 7 is a sectional elevational view showing how the deviceaccording to the invention is used for sampling the liquid to beexamined;

[0034]FIG. 8 is a similar view showing how the device in accordance withthe invention is drained, after a sample has been taken, by means of asyringe;

[0035]FIG. 9 is the corresponding top view, a second possible locationfor the syringe being shown with a syringe partially illustrated;

[0036]FIG. 10 is a view similar to FIG. 8, where the drainage isperformed with a vacuum flask;

[0037]FIGS. 11 and 12 are sectional elevational views showing how thelatching tabs are broken off the intake body in order to release thelatter from the drainage body;

[0038]FIG. 13 shows how the membrane is recovered with tweezers afterthis release; and

[0039]FIG. 14 shows how the membrane is deposited in a Petri dish.

[0040] The device 1 for microbiological examination of a sample ofliquid under pressure shown in the drawings, and notably in FIGS. 1 and2, has in general terms a symmetry of revolution around a central axis.It has an intake body 2, a drainage body 3 and a filtering membrane 4.

[0041] The intake body 2 has a reservoir 5, a skirt 6 which is connectedexternally to the reservoir 5 and four latching tabs 7 which extendprojecting from the skirt 6, in an axial direction.

[0042] The reservoir 5 has an end wall 8 and a lateral wall 9.

[0043] Two diametrically opposite pipes 10 extend projecting outwardfrom the lateral wall 9, above the skirt 6, each of these pipesconstituting a female Luer connector adapted to receive internally amale Luer connector, as will be explained below with the help of FIG. 7,the passage internal to each pipe 10 being continued by an aperture 11made in the wall 9, this aperture being in immediate proximity to theend wall 8.

[0044] The lateral wall 9 finishes at the end opposite the end wall 8 inan edge forming part of a seal 13, a groove 14 being made to that effectin the rigid part of the wall 9, as will be explained in more detailsubsequently with the help of FIGS. 2, 3 and 6.

[0045] The skirt 6 is connected to the reservoir 5 by the outside of thelateral wall 9, at a level situated between the groove 14 and the pipes10, the skirt 6 having a truncated-cone shaped wall 15 and a cylindricalwall 16, the skirt 6 being connected to the wall 9 by the small-diameterend of the wall 15 while the connection between the walls 15 and 16 ismade by the large-diameter end of the wall 15, the connection betweenthe walls 15 and 16 being situated approximately at the level of theedge of the wall 9.

[0046] Each of the latching tabs 7 has a general outline in the form ofa trapezium symmetrical with respect to the axial direction, the sideforming the free end 18 of the tab 7 being parallel to the one by whichthis tab is connected to the skirt 6, and more precisely to the edge ofthe wall 16, the tab 7 narrowing steadily between its connection to theskirt 6 and its free end.

[0047] On either side of each tab 7, a notch 17 is made in the wall 16,over a certain distance from the edge thereof.

[0048] Each tab 7 has, from its free end 18, an internal surface 19which is straight, that is to say parallel to the axial direction, asfar as a dihedral 20 from which the surface 19 is inclined inward andtowards the wall 16.

[0049] As for the external surface 21 of each tab 16, this is inclinedoutward and towards the wall 16, the surface 21 extending between thesurface 18 and a transversely oriented surface 22 which connects thesurface 21 and a groove 23 situated between an external shoulder 24whose surface 22 constitutes the edge and a surface 25 offset inwardwith respect to the surface 21, the surface 25 being in the continuationof the external surface of the wall 16.

[0050] It should be noted that the portion of each tab 7 situatedbetween the bottom of the groove 23 and the edge of the wall 16 has athickness which is a minimum at the level of the dihedral 20.

[0051] Consequently, it is in the region of the dihedral 20 that the tab7 breaks if a sufficiently large pressure is exerted on the surface 21,and more generally if there is exerted on the tab 7 a radial forcedirected inward, the force necessary for breaking the tab 7 beingsmaller the closer it is applied to the end surface 18.

[0052] As can be seen more particularly in FIG. 1, the surface 21 hasedges parallel to the axial direction, each tab 7 having a notch 26 withan L-shaped profile between the lateral edges of the surface 21 and thelateral edges of the tab 7.

[0053] As can be seen better in FIG. 4, the drainage body 3 has acircular table 30 and a skirt 31 disposed in a step around the table 30.

[0054] The latter has an annular transverse wall 32 delimited on theopposite side from the skirt 31 by a surface 33 which is flat in themain but having a slight bevel towards the outside.

[0055] The internal periphery of the wall 32 is connected to a wall 34delimited, on the side of the surface 33, by a surface 35 which isconcave in the main, offset with respect to the surface 32 in the axialdirection, towards the skirt 31, the perimeter of the surface 35 and theinternal periphery of the surface 33 being connected by a slightlytruncated-cone shaped surface 36.

[0056] The wall 34 is connected centrally to a pipe 37 whose internalpassage is extended into the wall 34 by an output aperture 38,concentric drainage channels 39 being put into the wall 34 from thesurface 35, radially oriented channels (not visible in the drawings)also being made, with the same depth as the channels 39, these radialchannels opening of course into the output aperture 38, through which,therefore, there flows out all the liquid drained by the channels madein the wall 34 hollowed out with respect to the surface 35.

[0057] At the junction between the walls 32 and 34 there is situated anannular rib 40 which projects with respect to the walls 32 and 34 on theside of the skirt 31, this rib tapering towards its free end in aV-shaped profile, so that this end constitutes a sharp edge.

[0058] The table 30 also has a tubular lateral wall 41 which isconnected by one end to the wall 32 while, by the other end, it isconnected to the skirt 31.

[0059] The latter has a transversely oriented annular wall 42 and anaxially oriented cylindrical wall 43, the wall 42 being connected by oneof its ends to the wall 41 and by the other to the wall 43.

[0060] In the wall 42, in proximity to the wall 41, four openings 44 aremade, which have between them the same angular spacing as between thelatching tabs 7, that is to say they are spaced out from one another by90°, these openings having an outline corresponding to the largestoutline of the tabs 7, so that the latter can each pass through arespective opening 44.

[0061] Each opening 44 is bordered on the external side by an axiallyoriented tooth 45 projecting on the opposite side from the table 30.

[0062] Each tooth 45 extends projecting over a height corresponding tothe depth of the groove 23 and has a thickness less than the width ofthe groove 23, the distance separating each tooth 45 from the wall 43being greater than the thickness of the shoulder 24 (see FIG. 5).

[0063] At the level of each opening 44, the wall 43 has a notch 46 ofgeneral rectangular form with rounded corners, extending overapproximately two thirds of the height of the wall 43 and over a widthwhich is approximately twice the width of the latching tabs 7.

[0064] The wall 43 also has four notches 47, each disposed halfwaybetween two successive notches 46, the notches 47 having a rounded formwhose maximum height corresponds approximately to one third of theheight of the wall 43.

[0065] The drainage body 3 also has a porous pad 48 (not depicted inFIG. 4), which has a constant thickness with two opposite surfaces ofthe same form as the surface 35, its diameter and thickness being thesame as those of the surface 36.

[0066] When the filtration body 2, the drainage body 3 and the membrane4 are assembled, as shown notably in FIGS. 1 and 2, the membrane 4 isgripped between the edge of the lateral wall 9 of the reservoir 5 of theintake body 2 and the surface 33 of the wall 32 of the circular table 30of the drainage body 3, the bodies 2 and 3 being locked to one anotherby virtue of the latching tabs 7 and the skirt 31, which are mutuallydisposed as can be seen more particularly in FIG. 5.

[0067] It should be noted that the tooth 45 of the wall 42 fits into thegroove 23 of the tab 7 and that the shoulder 24 of this tab fits intothe space situated between the wall 43 and the tooth 45, so that thecooperation between the shoulder 24 and the tooth 45 provides anextremely powerful locking of the tab 7 in the skirt 31, capable ofwithstanding relatively large forces tending to move the bodies 2 and 3away from one another.

[0068] It should also be noted that the end 18 of the tab 7 is recessedwith respect to the free end of the wall 43, so that, when the device 1is put down on a surface with the drainage body 3 at the bottom, it isby means of the skirt 31 thereof that the device 1 rests on thissurface, no force being exerted for this reason on the tabs 7, whichtherefore do not risk being broken accidentally.

[0069] As can be seen in FIG. 2, when the device 1 is assembled, theseal 13, and more particularly the cushion thereof, is highly compressedcompared with the off-load form of this seal shown in FIG. 6.

[0070] As indicated above, this seal has a T-shaped general profilewhose longitudinal branch forms a rib 50 designed to be inserted intothe groove 14 and whose transverse branch forms a cushion 51 designed toenter into contact with the membrane 4.

[0071] The free end of the cushion 51 has a central slot 52 which makesit possible to release two annular lips 53 allowing the best cooperationof the cushion 51 with the membrane 4.

[0072] It should be noted that the junction between the rib 50 and thecushion 51 is made by a straight surface on the internal side while, onthe external side, there is a bevel 54.

[0073] This bevel in fact corresponds to a chamfered lip 55 at theexternal periphery of the end of the rigid part of the wall 9, thischamfered lip making it possible to laterally contain the cushion 51 onthe external side in order that it flows mainly inward, that is to saytowards the chamber delimited by the membrane 4 and the reservoir 5.

[0074] The intake body 2 is obtained, with the exception of the seal 13,by moulding of a relatively rigid and transparent plastic, and thenthere is moulded, on to this piece, the seal 13, which is made ofelastomer, this over-moulding being carried out in the exampleillustrated by bi-injection.

[0075] The part of the drainage body 3 depicted in FIG. 4 is also madeof relatively rigid moulded plastic, here white in colour, this partbeing next equipped, by simple fitting, with the porous pad 48.

[0076] In order to assemble the intake body 1, the drainage body 3 andthe membrane 4, the latter is put on the table 30, concentricallytherewith, then the intake body 2 is positioned facing the drainage body3 with the latching tabs 7 aligned with the openings 44, then the body 2is pressed hard towards the body 3 so that the tabs 7 engage in theopenings 44 flexing slightly by virtue of the inclined surface 21 whichacts as a ramp, the force exerted allowing the surface 22 of theshoulder 24 to get over the tooth 45 at the end of the pushing inmovement, by virtue of the spring of the tabs 7, the seal 13 nextrelaxing slightly so that the play between the tabs 7 and the skirt 31is completely taken up, the elasticity of the seal 13, which is thencompressed, maintaining the locking thus obtained.

[0077] It should be noted that the maintaining of the seal in thecompressed state allows it to offer excellent sealing between themembrane 4 and the edge of the wall 9, and furthermore, by reaction,between the membrane 4 and the surface 33.

[0078] It should also be noted that the internal surface of the wall 16has localized areas of extra thickness 27 (FIG. 3) coming into contactwith the external surface of the wall 41, which provides a lateralwedging between these surfaces, which are of similar diameter, and moregenerally between the bodies 2 and 3.

[0079] Finally it should be noted that, once the device 1 has beenassembled in this way, it is possible to package it and sterilize itwith a gas such as ETO or by irradiation.

[0080] Of course, before packaging the assembled device 1 andsterilizing it, each of the pipes 10 and 37 is equipped with a stopper.

[0081] There will now be explained how the sampling of a liquid underpressure is carried out with the device 1.

[0082] First of all the stopper blocking off one of the pipes 10 and thestopper blocking off the pipe 37 are removed, then the unstoppered pipe10 is connected to a source of liquid under pressure, for example using,as shown in FIG. 7, a sampling connector 60 having a male Luer tip 61,which is inserted into the passage of the unstoppered pipe 10 and thevalve 62 of the connector 60 is manipulated, so that the chamber formedby the reservoir 5 and the membrane 4 is raised to the same pressure asthe liquid, for example 3 bars, the liquid entering the reservoir 5through the aperture 11 and leaving the reservoir by passing through themembrane 4, which comes to rest on the porous pad 48, the liquid whichhas passed through the membrane 4 being guided by the channels 39 to theaperture 38, the liquid leaving the device 1 by the pipe 37, a graduatedcontainer being preferably disposed under the device 1 in order torecover the liquid coming out of the pipe 37 in order to know when thevolume required for the sample has passed through the membrane 4.

[0083] When this volume has been reached, the valve 62 is closed and thedevice 1 is removed from the connector 60, then there is put in place,in the unstoppered pipe 10, an air sterilization filter 63 (depicted inFIG. 10 but not in FIG. 8), and the drainage of the liquid still presentnotably in the reservoir 5 is next carried out, by suction through theoutput aperture 38.

[0084] In the example shown in FIG. 8, the drainage is performed with asyringe or pump 64 having a connector 65 provided with a suction tip 66which has been inserted into the passage of the pipe 37, the liquidsucked out by the tip 66 being expelled by the tip 67 when the shaft 69is pushed into the body 68, by pressing on the plunger 70.

[0085] It should be noted that the notches 47 made in the wall 43 makeit possible to correctly position the pump or syringe 64 in relation tothe device 1, in four positions at 90° from one another, two of thesepositions being shown in FIG. 8.

[0086] Another possibility for extracting the liquid remaining in thedevice 1 after sampling, is to use a vacuum flask, as shown in FIG. 10.

[0087] The vacuum flask 71 illustrated has a glass body 72 having, atthe level of its neck, a pipe 73 connected, in a manner not depicted, toa vacuum pump, and, at the top of this neck, a flexible stopper 74 witha central aperture 75 made in it, the flask 71 being of a type which iscommonly found in practice.

[0088] The device 1 is simply put down on the stopper 74, with the pipe37 engaged in the aperture 75 and the rib 40 supported on the top of thestopper 74.

[0089] On account of the tapered profile of the rib 40, the latterlocally deforms the stopper 74 and provides sealing which makes itpossible to suck out the residual liquid, as drawn.

[0090] Once the liquid remaining in the device 1 has been emptiedtherefrom, the device 1 can be opened, which is performed by breakingthe four latching tabs 7, by simple pressure on said tabs through therespective notches 46, as explained above and illustrated in FIGS. 11and 12.

[0091] It is then possible to remove the intake body 2 from the drainagebody 3 and pick up the membrane 4, for example with sterile tweezers 80,as shown in FIG. 13, then deposit the membrane through which the sampleto be examined has passed, in a Petri dish 81, as shown in FIG. 14, thencarry out conventionally the incubation of the membrane/Petri dishassembly.

[0092] It should be noted that the concavity of the surface 35 has beencalculated so that the ratio of the difference between the length of thearc corresponding to the profile, in a diametral plane, of the surfaceof the pad 48 facing the membrane 4 and between the length of the chordof this arc, over the latter length, corresponds to the coefficient ofexpansion of the membrane 4 between the dry state and the wet state.

[0093] The result thereof is that the expansion of the membrane 4, whenit changes from the dry state to the wet state, corresponds precisely tothe difference in length between the arc corresponding to theabove-mentioned profile and the chord of this arc, so that, in the wetstate, the membrane 4 rests perfectly on the pad 48, with no creases.The pad 48 therefore provides a particularly effective support for themembrane 4 when it is subjected to the difference in pressure whichallows the liquid to flow through it.

[0094] Moreover, when the user recovers the membrane 4 with the tweezers80 as shown in FIG. 13, this membrane has a concave form, on the sidewhere the reservoir 5 is situated, that is to say on the side where anymicro-organisms retained by the membrane at the time of sampling arepresent, the curvature of the membrane 4 thus being in the correctdirection where putting it down on the surface of the culture medium 82in the dish 81 is concerned.

[0095] This is because, when the membrane 4 is positioned on the dish81, it is the convex side of the membrane, 4 which faces the surface ofthe medium 82, so that, putting down the membrane 4 on the medium 82from a portion of the membrane opposite the tweezers 80 and moving themso that the membrane progressively comes into contact with the medium 82to the place where it is held by the tweezers. The risk that themembrane has one or more hollows on the opposite side from the medium82, and therefore the risk that it develops one or more pocket(s) of airbetween the membrane 4 and the medium 82, are thus zero or at any rateminimal.

[0096] The culture medium 82 in the dish 81 illustrated in FIG. 14 is aculture medium containing agar-agar, used in the solid state afterhaving been poured into the dish hot.

[0097] If it is wished to use a liquid culture medium, it is possible toreplace the Petri dish 81 with a similar dish but one where theagar-agar culture medium 82 is replaced by an absorbent pad impregnatedwith liquid culture medium.

[0098] Another possibility, rather than culturing the micro-organismsoutside the device 1, is to inject liquid culture medium therein usingone of the pipes 10, then to drain the excess culture medium using thepipe 37, and to next put the device 1 to incubate directly, the membrane4 being recovered only in order to identify and count themicro-organisms after incubation.

[0099] In such a case, there is an advantage in using a liquid culturemedium which is slightly more concentrated than the conventional mediasince there always remains, notably in the pad 48, a certain amount ofthe sampled liquid which mixes with the injected culture medium which istherefore diluted.

[0100] In variants, not depicted, it is the drainage body 3, and not theintake body 2, which has the elastomer seal such as the seal 13described above; the male and female latching elements between thebodies 2 and 3 are provided respectively on the drainage body 3 and theintake body 2, rather than the reverse; and/or use is made of latchingmeans of different type, locking means having hinge means between thebodies 2 and 3 and latching means opposite the hinge means, or means oflocking other than by latching.

[0101] Many other variants are possible depending on circumstances, andit should be stated in this respect that the invention is not limited tothe examples described and depicted.

1. Device for microbiological examination of a sample of liquid underpressure, having an intake body, a filtering membrane and a drainagebody, said intake body having a reservoir, in one wall of which a liquidinput aperture is made, said membrane closing said reservoir, saiddrainage body having means of supporting said membrane on the oppositeside from said reservoir and a liquid output aperture, said intake bodyand said drainage body having integrally moulded mutual locking means;characterised in that said membrane (4) is gripped annularly at theperiphery between a first member (9) forming part of said intake body(2) and a second member (32) forming part of said drainage body (3) withone out of said first member and said second member having an elastomerseal (13) by means of which it comes into contact with said membrane(4), and in that said locking means (7, 31) are adapted to allow theopening of said device by requiring only a separation movement betweensaid first member (9) and said second member (32).
 2. Device accordingto claim 1, characterised in that the membrane (4) is held exclusivelyon account of it being gripped annularly at the periphery between saidfirst member (9) and said second member (32).
 3. Device according toeither one of claims 1 or 2, characterised in that said seal (13) ismoulded on to that one out of said first member (9) and said secondmember (32) which includes it.
 4. Device according to any one of claims1 to 3, characterised in that it is the first member (9) which has saidelastomer seal (13).
 5. Device according to claim 4, characterised inthat said first member (9) forms a lateral wall of said reservoir (5) ofthe intake body (2), said wall (9) finishing at one end in an edgeforming part of said seal (13).
 6. Device according to claim 5,characterised in that a groove (14) is made at the end of a rigid partof said lateral wall (9) while said seal (13) has a T-shaped profilewhose longitudinal branch forms a rib (50) inserted into said groove(14) and whose transverse branch forms a cushion (51) which is incontact with the membrane (4).
 7. Device according to claim 6,characterised in that there is a bevel (54) between the rib (50) and thecushion (51) on the external side, while, on the internal side, the rib(50) and the cushion (51) are connected by a straight surface.
 8. Deviceaccording to either one of claims 6 or 7, characterised in that saidcushion (51) has two annular lips (53).
 9. Device according to any oneof claims 1 to 8, characterised in that said locking means have means ofaxial latching (7, 31) between the intake body (2) and the drainage body(3).
 10. Device according to claim 9, characterised in that one out ofsaid intake body (2) and said drainage body (3) has at least one axiallyoriented latching tab (7) while the other has means of receiving (42,44, 45) said latching tab.
 11. Device according to claim 10,characterised in that said latching tab is connected to the remainder ofthat one out of said intake body (2) and said drainage body (3) whichincludes it, by a breakable zone.
 12. Device according to claim 11,characterised in that said breakable zone is situated in the region of adihedral (20) in one of the surfaces (19) of said latching tab (7). 13.Device according to claim 12, characterised in that said surface (19)having a dihedral (20) is situated on the internal side of the latchingtab (7).
 14. Device according to any one of claims 10 to 13,characterised in that said latching tab (7) extends projecting from theedge of a skirt (6) forming part of that one out of said intake body (2)and said drainage body (3) which includes it.
 15. Device according toclaim 14, characterised in that that one out of said intake body (2) andsaid drainage body (3) which has means of receiving said latching tab(7) has a wall (42) oriented transversely and provided with an opening(44) through which the latching tab (7) can pass, said tab and said wall(42) having means (23, 24, 45) for preventing the withdrawal of the tab(7) once it has been pushed right into the opening (44).
 16. Deviceaccording to claim 15, characterised in that said means for preventingthe withdrawal of the latching tab (7) have, on said wall (42), a tooth(45) oriented axially and bordering said opening and having, on saidlatching tab, a groove (23) adapted to accommodate said tooth (45). 17.Device according to either one of claims 15 or 16, characterised in thatsaid transversely oriented wall (42) is connected to a lateral wall (43)extending on the opposite side from that one out of said intake body (2)and said drainage body (3) which has the latching tab (7), with thedimension in the axial direction of said lateral wall (43) being greaterthan the dimension in the axial direction of the latching tab (7). 18.Device according to claim 17, characterised in that a notch (46) is madein said lateral wall (46) at the level of said opening (44), to make itpossible to press on said latching tab (7).
 19. Device according to anyone of claims 10 to 18, characterised in that it is the intake body (2)which has the latching tab (7), and in that it is the drainage body (3)which has the means of receiving (42, 44, 45) said latching tab (7). 20.Device according to any one of claims 10 to 19, characterised in thatone out of said intake body (2) and said drainage body (3) has a numberof said latching tabs (7).
 21. Device according to claim 20,characterised in that it has four latching tabs (7).
 22. Deviceaccording to any one of claims 9 to 21, characterised in that saidlocking means comprise exclusively said axial latching means (7, 31).23. Device according to any one of claims 1 to 22, characterised in thatsaid drainage body (3) has a circular table (30) provided at its centrewith means of supporting (48) said membrane (4) and having, around saidsupport means (48), a wall (32) having a surface (33) situated facingsaid elastomer seal (13), which forms part of said intake body (2), saidmembrane (4) being squeezed between said surface (33) and said seal(13).
 24. Device according to claim 23, characterised in that saidsupport means (48) have a concave surface facing said membrane (4). 25.Device according to claim 24, characterised in that the ratio of thedifference between the length of the arc corresponding to the profile,in a diametral plane, of said surface of said support means (48) andbetween the length of the chord of this arc, over the latter length,corresponds to the coefficient of expansion of said membrane (4) betweenthe dry state and the wet state.
 26. Device according to any one ofclaims 23 to 25, characterised in that said support means are formed bya porous pad (48).
 27. Device according to claim 26, characterised inthat said drainage body (3) has drainage channels (39) under said porouspad (48), said drainage channels opening into said output aperture (38).28. Device according to any one of claims 23 to 27, characterised inthat the external diameter of said circular table (30) correspondssubstantially to the internal diameter of a skirt (6) included in saidintake body (2), said skirt (6) encircling said circular table (30). 29.Device according to claim 28, characterised in that areas of extrathickness for wedging (27) are provided between said circular table (30)and said skirt (6).
 30. Device according to any one of claims 23 to 29,characterised in that said drainage body has a skirt (31) disposed in astep with respect to said circular table (30).
 31. Device according toclaim 30, characterised in that said skirt (31) has means of latching(42, 44, 45) with said intake body (2).
 32. Device according to eitherone of claims 30 or 31, characterised in that said skirt (31) of thedrainage body (3) has at least one notch (47) adapted to allow theplacing of a drainage syringe (64).
 33. Device according to any one ofclaims 1 to 32, characterised in that said output aperture (38) of thedrainage body (3) is in the continuation of the internal passage of acoaxially disposed output pipe (37).
 34. Device according to claim 33,characterised in that said drainage body (3) has, around said outputpipe (37), an annular rib (40) tapering towards its end.
 35. Method fordraining a device according to claim 34, characterised in that it isplaced on a vacuum flask (71) with said output pipe (37) engaged in thecentral hole (75) of the stopper (74) of said flask and said annular rib(40) resting on this stopper.